GB2059080A - Measuring ionic beam current - Google Patents
Measuring ionic beam current Download PDFInfo
- Publication number
- GB2059080A GB2059080A GB8023149A GB8023149A GB2059080A GB 2059080 A GB2059080 A GB 2059080A GB 8023149 A GB8023149 A GB 8023149A GB 8023149 A GB8023149 A GB 8023149A GB 2059080 A GB2059080 A GB 2059080A
- Authority
- GB
- United Kingdom
- Prior art keywords
- measuring surface
- measuring
- auxiliary electrode
- magnet means
- ions
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/29—Measurement performed on radiation beams, e.g. position or section of the beam; Measurement of spatial distribution of radiation
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/08—Measuring current density
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/02—Details
- H01J37/244—Detectors; Associated components or circuits therefor
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
- H01J37/317—Electron-beam or ion-beam tubes for localised treatment of objects for changing properties of the objects or for applying thin layers thereon, e.g. for ion implantation
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
- H01J2237/244—Detection characterized by the detecting means
- H01J2237/24405—Faraday cages
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
- H01J2237/244—Detection characterized by the detecting means
- H01J2237/2449—Detector devices with moving charges in electric or magnetic fields
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
- H01J2237/245—Detection characterised by the variable being measured
- H01J2237/24507—Intensity, dose or other characteristics of particle beams or electromagnetic radiation
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- High Energy & Nuclear Physics (AREA)
- Molecular Biology (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Measurement Of Radiation (AREA)
- Physical Vapour Deposition (AREA)
Abstract
The apparatus includes an auxiliary electrode (5) situated upstream of the plane containing the measuring surface (2), and magnet means (3) for setting up a magnetic field extending transversely to the stream of ions. The magnet means (3) is spaced from the measuring surface, has a conducting surface on at least that part facing the measuring surface and the auxiliary electrode (5) is interposed and at least partly surrounds the space between the measuring surface (2) and the magnet means (3). At least the outer surface of the magnet means (3) facing the measuring surface (2) is electrically conductive. The apparatus includes a device (10) for measuring the currents flowing via the measuring surface (2), auxiliary electrode (5) and magnet means (3). <IMAGE>
Description
SPECIFICATION
An apparatus for measuring ionic current impinging in vacuum on to a measuring surface
The invention relates to an apparatus for measuring ionic current impinging in vacuum on to a measuring surface.
Apparatus of this kind is used in a number of modern appliances in which ionic current flows in a free space in vacuum. When surfaces are treated with ions, it is e.g. important to know the ionic current or the ionic current density (ionic current divided by the area entered by the current) to carry out the method with guaranteed results. Also the knowledge of the total number of ions impinging on to a surface, the so-called ion dose, is important which is obtained from the ionic current by integration over a period of time. A modern field of use of the measurement of ionic current is the ion implantation technology. The physical properties of the interface of a body altered by ion implantation depend to a high degree on the ion dose.The measurement of ionic current density (A/cm2) can be achieved by the measurement of the electric current which may be obtained from a probe of predetermined measuring surface on which impinge the ions. According to the present state of the art intensities of the ionic currents in the range of lO to 10-3 A are mostly used. If as a result of ion bombardment of the measuring surface a plasma is formed or if the surface emits secondary electrons special provisions are needed for accurate measurement. The measurement is made difficult mainly by the fact that the emission of secondary electrons depends, apart from the material of which the measuring surface is made, also on its temperature and the residual gas pressure in the vacuum chamber.The measuring error caused by the secondary electrons consists substantially in that the ionic current seems to be increased by them. If, on the other hand, an electronic circuit having a high inlet resistant is used for the measurement (integration), the measuring surface is charged positively by the impinging positive ions which partially suppresses the emission of secondary electrons which again decreases the measured ionic current.
It is generally known to arrange around the measuring surface a Faraday shield to suppress the effect of secondary electrons. There may be, however, problems when it is not possible, e.g. in manufacturing installations, to install, due to lack of space, the Faraday shield in the immediate vicinity of the measuring surface. The simplest way is to provide an auxiliary electrode which surrounds the measuring surface and largely suppresses emission of secondary electrons if it is sufficiently negatively precharged.
It is also known that a magnetic field of the order of about 100 gauss which is transverse to the direction of the ionic current helps to suppress emission of secondary electrons so that a Faraday shield or other kind of shielding electrode need not be used. Magnetic fields were found useful the lines of force of which emerge from and return to the measuring surface, while secondary electrons remain trapped in the "tunnel" formed by the arcs of the lines of force above the measuring surface or are forced to return to the measuring surface.
The term "measuring surface" is used in this specification to mean also parts of surfaces of work-pieces or substrates treated by ions while the impinging of ions on to the surface is to be measured.
As mentioned, the above described known devices cannot be used when there is no space immediately before the measuring surface for larger electrodes or magnets. This is often the case when the apparatus for the measuring of the ionic current is intended to be built into an existing appliance.
Measuring errors may be caused also by electrons which do not originate, as the secondary electrons, in the measuring surface but in the residual gas which is partly ionized by the ion beam. If the "extraneous" electrons reach the measuring surface they seemingly reduce the ionic current.
The problem to be solved by the present invention is to devise an apparatus which can be used to measure with high accuracy ionic current impinging on to a measuring surface in vacuum, while avoiding measuring errors caused by electrons, without requiring magnets positioned very close to the measuring surface.
This problem is solved by apparatus according to
Claim 1.
Space becomes available, thanks to the arrangement of the magnets at a greater distance from the measuring surface according to the invention, so that stronger magnets having a better screening effect may now be used. In addition it is also easier to make the carrier of the measuring surface movable, e.g. as a rotating drum, on the inner side of which are fixed the workpieces to be treated. Finally it is a further advantage of an apparatus according to the invention that when stronger electromagnets are used their possible heating does not cause, due to the increased distance, heating of the workpieces which can in any case thanks to the available space be better checked by corresponding cooling means.
One embodiment of the invention will now be described in greater detail with reference to the accompanying drawing. The drawing shows di agrammaticallythe arrangement of the parts which are essential for the measurement. The arrangement is situated in a vacuum chamber in which ion measurement should take place, e.g. in an ion implantation appliance.
The drawing shows the substrate carrier 1 with a substrate attached thereto, on the surface 2 of which, which serves as a measuring surface, impinges the ionic current in a direction indicated by an arrow. At a distance before the plane containing the measuring surface, preferably at such a distance a that the ratio alb where b is the shortest extension of the auxiliary electrode transverse to the direction of movementofthe impinging ions, greater than 1/3, or even better greater than 1/2, are situated both the magnets 3 (which are held in the vacuum chamber by holders not illustrated in the diagrammatic draw ing). The drawing shows also an auxiliary electrode 5, situated between the measuring surface 2 and the magnets 3.This electrode 5 may be in two parts, it may consist e.g. of an upper and a lower plate, both the plates surrounding at least partly the space between the magnet and the measuring surface. The electrodes may also be in the shape of a cylindrical jacket and may surround that space, except for a possible gap, nearly fully. The smallest distance between the two plate electrodes or the diameter of the jacket-shaped auxiliary electrode represents then the shortest extension b of the auxiliary electrode transverse to the direction of the impinging ions in the sense of Claim 2.
All the auxiliary electrodes may be arranged in the vacuum chamber either unsupported or they may be attached to the magnets orto the workpiece carrier or even to the workpieces themselves. In the last two cases they move together with the carrierorwork- pieces so that a plurality of workpieces may be brought in succession into the ion beam and treated.
The drawing shows also a diaphragm 8which serves to screen magnets and auxiliary electrodes from bombardment by ions and limits the crosssection of the beam on to the surfaces to be treated.
The magnets 3, which set up the magnetic field transverse to the direction of impinging of currents, may be iron magnets or they may be of ceramic magnetic materials. In each case it is important that the side of the magnet facing the stream of secondary electrons issuing from the measuring surface should have an electrically conductive surface, which iron magnets provide without any special provision or which may be obtained by a metallic cover7.
The ionic current is measured by the described apparatus by detecting the sum of the currents flowing through the measuring surface and all auxiliary electrodes and magnets and possibly their covers, taking into consideration their sign. The measurement of these currents may be made at separate current collectors 9 or, in the simplest way, in that these collectors are brought together and the total current is measured by a single instrument 10.
A particular advantage of the described apparatus lies in that extraneous electrons, which move together with the ions in the direction to the measuring surface, are kept away from this surface in that they are deflected by the magnetic field, which is situated sufficientlyfarfrom the measuring surface (assuming that the field is strong enough), the deflection being such that they can reach neither the measuring surface nor the auxiliary electrodes or magnets and so tamper with the measurement.
Claims (6)
1. An apparatus for measuring ionic current of a stream of ions impinging in vacuum on to a measuring surface, the apparatus including an auxiliary electrode situated upstream of the plane containing the measuring surface, and magnet means for setting up a magnetic field extending transversely to the stream of ions, wherein the magnet means is spaced from the measuring surface, and the auxiliary electrode is interposed and at least partly surrounds the space between the measuring surface and the magnet means, at least that outer surface of the magnet means which faces the measuring surface is electrically conductive, and the apparatus includes a meter for measuring the currents flowing via the measuring surface, auxiliary electrode and magnets.
2. An apparatus according to Claim 1 wherein the ratio alb of the distance a of the central plane of the magnetic field from the measuring surface to the shortest transverse dimension b of the auxiliary electrode is greater than 1/3.
3. An apparatus according to Claim 2 wherein the ratio alb is greater than 1/2.
4. An apparatus according to any one of Claims 1 to 3 wherein the auxiliary electrode is connected to the magnet.
5. An apparatus according to any one of Claims 1 to 3 wherein the auxiliary electrode is connected to a carrier of the measuring surface.
6. An apparatus for measuring ionic current of a stream of ions impinging in vacuum on to a measuring surface constructed, arranged and adapted to operate substantially as herein described with reference to, and as shown in, the accompanying drawing.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH691979 | 1979-07-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2059080A true GB2059080A (en) | 1981-04-15 |
Family
ID=4317103
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8023149A Withdrawn GB2059080A (en) | 1979-07-26 | 1980-07-16 | Measuring ionic beam current |
Country Status (4)
| Country | Link |
|---|---|
| DE (1) | DE3025550A1 (en) |
| FR (1) | FR2462718A1 (en) |
| GB (1) | GB2059080A (en) |
| NL (1) | NL8004026A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103176202A (en) * | 2013-04-12 | 2013-06-26 | 中国工程物理研究院核物理与化学研究所 | Device and method for measuring components of deuterium ion beam of deuterium-tritium neutron tube |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5113074A (en) * | 1991-01-29 | 1992-05-12 | Eaton Corporation | Ion beam potential detection probe |
-
1980
- 1980-07-05 DE DE19803025550 patent/DE3025550A1/en not_active Withdrawn
- 1980-07-11 NL NL8004026A patent/NL8004026A/en not_active Application Discontinuation
- 1980-07-16 GB GB8023149A patent/GB2059080A/en not_active Withdrawn
- 1980-07-24 FR FR8016380A patent/FR2462718A1/en not_active Withdrawn
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103176202A (en) * | 2013-04-12 | 2013-06-26 | 中国工程物理研究院核物理与化学研究所 | Device and method for measuring components of deuterium ion beam of deuterium-tritium neutron tube |
| CN103176202B (en) * | 2013-04-12 | 2014-12-10 | 中国工程物理研究院核物理与化学研究所 | Device and method for measuring components of deuterium ion beam of deuterium-tritium neutron tube |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2462718A1 (en) | 1981-02-13 |
| DE3025550A1 (en) | 1981-02-12 |
| NL8004026A (en) | 1981-01-28 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |